The present invention relates to wireless digital networks, and more particularly, to the problem of managing addresses assigned to clients through DHCP.
Data networks, particularly wireless data networks, have become an expected or necessary resource in more and more situations. Once present only in the workplace environment, they are now nearly ubiquitous, present in schools, libraries, retail environments, and just about anyplace where people gather.
Operating wireless networks, particularly in environments handling large numbers of users and/or devices present a number of challenges. The operating environment has changed dramatically within the last few years, from a user having a single device such as a laptop computer with wireless capability, to a single user having multiple devices each with such capability, such as laptops, smart phones, tablets, and portable music players.
To work with a local wireless network, a device first uses the DHCP protocol to request an address which the device will use while associated to the network. This address is supplied by a DHCP server. The number of distinct addresses available to the DHCP server is determined by its configuration and is finite. A DHCP server is considered to own the IP addresses it manages, and leases them to clients. A DHCP server responds to requests by returning an address (if one is available) which is valid for a predetermined period of time, known as the DHCP lease time. DROP servers may also work through DHCP relays, which are used to administer subnets.
DHCP is known to the art, described for example in RFC 2131 for IPv4 networks, and described in RFC 3315, RFC 3633 and RFC 3736 for DHCPv6 in IPv6 networks.
Particularly in IPv4 environments where multiple users with multiple devices congregate, the finite number of distinct addresses available through a DHCP server may turn out to be a limiting factor in supporting users on the network.
It has also become apparent in monitoring such networks that while there may be a large number of devices associated to a network, only a fraction of those devices are active. Yet each associated device is tying up an address.
It is known to the art that in environments where the number of users may exceed the number of addresses available, short lease times should be used to free up unused addresses and make them available.
The seemingly simple and straightforward solution of having the DHCP server only grant short leases, two minutes, for example, does not work. To be motivated to attempt such a solution, one has to have a network environment in which users exceed available addresses; a very busy environment. In such an environment, issuing only short leases will result in an overloaded DROP server and network segments flooded with DHP traffic.
What is needed is a better way to manage DHCP leases.